The objective of these experiments is to characterize the mechanisms of synthesis and processing of mRNA in mammalian cells, using globin mRNA as a model mRNA. Pulse-labeled (radioactive) globin mRNA nucleotide sequences from mouse erythroid cells were found in a molecule that sedimented faster than cytoplasmic (non-radioactive, steady-state) globin mRNA in a denaturing sucrose gradient. The larger molecule was a precursor of globin mRNA, since pulse labeled globin mRNA nucleotide sequences in the larger molecule were "chased" into a globin mRNA-sized molecule during a 75 minute incubation in actinomycin D. The research proposed here is designed to investigate some of the properties of the mRNA precursor and its processing and to compare globin gene transcription in normal vs. neoplastic cells. These experiments propose to answer the following questions: 1) What is the precise molecular weight of the precursor? 2) Is cleavage accomplished in several steps that generate intermediate products, or does it occur in a single step? 3) How long does the cleavage reaction(s) take? 4) At what stage during cleavage are globin mRNA sequences polyadenylated? 5) What structural features are required for cleavage? 6) Are globin mRNA sequences transcribed in the same fashion in neoplastic (transformed) cells as in normal cells? Globin mRNA sequences will be identified by molecular hybridization analysis with globin complementary DNA. Pulse-labeled erythroid cell RNA will be fractionated by electrophoresis in polyacrylamide gels containing formamide. The molecular weight of the globin mRNA precursor and any intermediates will be compared in two mouse erythroid cells: fetal liver ("normal") and erythroleukemia (neoplastic).